A brief introduction to molecular orbital theory of simple polyatomic molecules for undergraduate chemistry students

A simple, four-step method for better introducing undergraduate students to the fundamentals of molecular orbital (MO) theory of the polyatomic molecules H2O, NH3, BH3 and SiH4 using group theory is reported. These molecules serve to illustrate the concept of ligand group orbitals (LGOs) and subsequent construction of MO energy diagrams on the basis of molecular symmetry requirements.

Final chlorine dioxide stage at near-neutral pH for bleaching eucalypt pulp

It is well known that pH is an important parameter for controlling the eucalyptus pulp bleaching when using the final chlorine dioxide stage, since it affects the effectiveness of the process. Recommendations found in the literature for operating are in the 3.5 to 4.0 range. However, in this paper it was shown that final chlorine dioxide has better performance, with significant brightness gain while also preserving pulp quality, when it is operated at near neutral pH. This result can be explained by the generation of sodium bicarbonate in situ upon adding carbon dioxide at this stage.

Thermal modelling of semiconductor switches in three-level Neutral Point Clamped Medium Voltage DTC-inverter

The aim of this thesis is to investigate the thermal loading of medium voltage three-level NPC inverter’s semiconductor IGCT switches in different operation points. The objective is to reach both a fairly accurate off-line simulation program and also so simple a simulation model that its implementation into an embedded system could be reasonable in practice and a real time use should become feasible. Active loading limitation of the inverter can be realized with a thermal model which is practical in a real time use. Determining of the component heating has been divided into two parts; defining of component losses and establishing the structure of a thermal network. Basics of both parts are clarified. The simulation environment is Matlab-Simulink. Two different models are constructed – a more accurate one and a simplified one. Potential simplifications are clarified with the help of the first one. Simplifications are included in the latter model and the functionalities of both models are compared. When increasing the calculation time step a decreased number of considered components and time constants of the thermal network can be used in the simplified model. Heating of a switching component is dependent on its topological position and inverter’s operation point. The output frequency of the converter defines mainly which one of the switching components is – because of its losses and heating – the performance limiting component of the converter. Comparison of results given by different thermal models demonstrates that with larger time steps, describing of fast occurring switching losses becomes difficult. Generally articles and papers dealing with this subject are written for two-level inverters. Also inverters which apply direct torque control (DTC) are investigated rarely from the heating point of view. Hence, this thesis completes the former material.

Evaluation of group electronegativities and hardness (softness) of group 14 elements and containing functional groups through density functional theory and correlation with NMR spectra data

Quantum Chemical calculations for group 14 elements of Periodic Table (C, Si, Ge, Sn, Pb) and their functional groups have been carried out using Density Functional Theory (DFT) based reactivity descriptors such as group electronegativities, hardness and softness. DFT calculations were performed for a large series of tetracoordinated Sn compounds of the CH3SnRR'X type, where X is a halogen and R and R' are alkyl, halogenated alkyl, alkoxy, or alkyl thio groups. The results were interpreted in terms of calculated electronegativity and hardness of the SnRR'X groups, applying a methodology previously developed by Geerlings and coworkers (J. Phys. Chem. 1993, 97, 1826). These calculations allowed to see the regularities concerning the influence of the nature of organic groups RR' and inorganic group X on electronegativities and hardness of the SnRR'X groups; in this case, it was found a very good correlation between the electronegativity of the fragment and experimental 119Sn chemical shifts, a property that sensitively reflects the change in the valence electronic structure of molecules. This work was complemented with the study of some compounds of the EX and ER types, where E= C, Si, Ge, Sn and R= CH3, H, which was performed to study the influence that the central atom has on the electronegativity and hardness of molecules, or whether these properties are mainly affected for the type of ligand bound to the central atom. All these calculations were performed using the B3PW91 functional together with the 6-311++G** basis set level for H, C, Si, Ge, F, Cl and Br atoms and the 3-21G for Sn and I atoms.

Leibniz's theory of bodies: monadic aggregates, phenomena, or both?

Leibniz's conception of bodies seems to be a puzzling theory. Bodies are seen as aggregates of monads and as wellfounded phenomena. This has initiated controversy and unending discussions. The paper attempts to resolve the apparent inconsistencies by a new and formally spirited reconstruction of Leibniz's theory of monads and perception, on the one hand, and a (re-)formulation and precisation of his concept of preestablished harmony, on the other hand. Preestablished harmony is modelled basically as a covariation between the monadic and the ideal realm.

Benjamin's conception of language and Adorno's aesthetic theory

According to the theory of language of the young Benjamin, the primary task of language isn't the communication of contents, but to express itself as a "spiritual essence" in which also men take part. That conception according to which language would be a medium to signification of something outside it leads to a necessary decrease of its original strength and is thus denominated by Benjamin bürgerlich. The names of human language are remainders of an archaic state, in which things weren't yet mute and had their own language. Benjamin suggests also that all the arts remind the original language of things, as they make objects "speak" in form of sounds, colors, shapes etc. That relationship between arts as reminders of the "language of things" and the possible reconciliation of mankind with itself and with nature has been developed by Theodor Adorno in several of his writings, specially in the Aesthetic Theory, where the artwork is ultimately conceived as a construct pervaded by "language" in the widest meaning - not in the "bourgeois" sense.

La cuestión del poder neutral en Schmitt

El artículo busca mostrar la importancia que la teoría del pouvoir neutre de B. Constant/ tuvo en la interpretación que Carl Schmitt hace de las funciones del Reichspräsident, en los años veinte hasta el nazismo. Aun cuando Schmitt critica al romanticismo, del cual al autor de Adolphe es una figura clave, igualmente reconoce que Constant teorizó la institución constitucional más adecuada para enfrentar las situaciones críticas, cuando la constitución debe autodefenderse mediante poderes legales pero excepcionales.

THE FORMAL AND THE FORMALIZED: THE CASES OF SYLLOGISTIC AND SUPPOSITION THEORY

As a discipline, logic is arguably constituted of two main sub-projects: formal theories of argument validity on the basis of a small number of patterns, and theories of how to reduce the multiplicity of arguments in non-logical, informal contexts to the small number of patterns whose validity is systematically studied (i.e. theories of formalization). Regrettably, we now tend to view logic 'proper' exclusively as what falls under the first sub-project, to the neglect of the second, equally important sub-project. In this paper, I discuss two historical theories of argument formalization: Aristotle's syllogistic theory as presented in the "Prior Analytics", and medieval theories of supposition. They both illustrate this two-fold nature of logic, containing in particular illuminating reflections on how to formalize arguments (i.e. the second sub-project). In both cases, the formal methods employed differ from the usual modern technique of translating an argument in ordinary language into a specially designed symbolism, a formal language. The upshot is thus a plea for a broader conceptualization of what it means to formalize.

Rebuilding Defenses: Explorations in Norman Fairclough’s Theory of Critical Discourse Analysis

Tutkielmassa eritellään Norman Faircloughin kriittisen diskurssianalyysin teoriaa ja siihen kohdistettua kritiikkiä. Pyrkimyksenä on sovittaa näitä erilaisia näkemyksiä keskenään ja tarjota ratkaisuja yhteen kiriittisen diskurssianalyysin keskeiseen ongelmaan eli emansipaation (sosiaalisten epäkohtien tunnistamisen ja ratkaisemisen) puutteellisuuteen. Teoriaosuudesta esiin nousevia mahdollisuuksia sovelletaan tekstianalyysiin. Tutkimuksen kohteena on teksti Rebuilding America’s Defenses: Strategy, Forces and Resources For a New Century ja jossain määrin sen tuottanut järjestö Project for the New American Century. Näitä tarkastellaan ennen kaikkea sosiaalisina ilmiöinä ja suhteessa toisiinsa. Faircloughin mallin suurimmiksi ongelmiksi muodostuvat perinteinen käsitys kielestä, jonka mukaan kielen järjestelmän abstraktit ja sisäiset suhteet ovat tärkeimpiä, sekä ideologinen vastakkainasettelu kritiikin lähtökohtana. Ensimmäinen johtaa kielellisten tutkimustulosten epätyydyttävään kykyyn selittää sosiaalisia havaintoja ja jälkimmäinen poliittiseen tai maailmankatsomukselliseen väittelyyn, joka ei mahdollista uusia näkemyksiä. Tutkielman lopputulema on, että keskittymällä asiasisältöön kielen rakenteen sijasta ja ymmärtämällä tekstin tuottaja yksittäisenä, rajattuna sosiaalisena toimijana voidaan analyysiin saada avoimuutta ja täsmällisyyttä. Kriittiinen diskurssianalyysi kaipaa tällaista näkemystä kielellisten analyysien tueksi ja uudenlaisen relevanssin löytääkseen.

Remarks on abstract Galois theory

This paper is a historical companion to a previous one, in which it was studied the so-called abstract Galois theory as formulated by the Portuguese mathematician José Sebastião e Silva (see da Costa, Rodrigues (2007)). Our purpose is to present some applications of abstract Galois theory to higher-order model theory, to discuss Silva's notion of expressibility and to outline a classical Galois theory that can be obtained inside the two versions of the abstract theory, those of Mark Krasner and of Silva. Some comments are made on the universal theory of (set-theoretic) structures.

The relation between the general maxim of causality and the principle of uniformity in hume's theory of knowledge

ABSTRACT When Hume, in the Treatise on Human Nature, began his examination of the relation of cause and effect, in particular, of the idea of necessary connection which is its essential constituent, he identified two preliminary questions that should guide his research: (1) For what reason we pronounce it necessary that every thing whose existence has a beginning should also have a cause and (2) Why we conclude that such particular causes must necessarily have such particular effects? (1.3.2, 14-15) Hume observes that our belief in these principles can result neither from an intuitive grasp of their truth nor from a reasoning that could establish them by demonstrative means. In particular, with respect to the first, Hume examines and rejects some arguments with which Locke, Hobbes and Clarke tried to demonstrate it, and suggests, by exclusion, that the belief that we place on it can only come from experience. Somewhat surprisingly, however, Hume does not proceed to show how that derivation of experience could be made, but proposes instead to move directly to an examination of the second principle, saying that, "perhaps, be found in the end, that the same answer will serve for both questions" (1.3.3, 9). Hume's answer to the second question is well known, but the first question is never answered in the rest of the Treatise, and it is even doubtful that it could be, which would explain why Hume has simply chosen to remove any mention of it when he recompiled his theses on causation in the Enquiry concerning Human Understanding. Given this situation, an interesting question that naturally arises is to investigate the relations of logical or conceptual implication between these two principles. Hume seems to have thought that an answer to (2) would also be sufficient to provide an answer to (1). Henry Allison, in his turn, argued (in Custom and Reason in Hume, p. 94-97) that the two questions are logically independent. My proposal here is to try to show that there is indeed a logical dependency between them, but the implication is, rather, from (1) to (2). If accepted, this result may be particularly interesting for an interpretation of the scope of the so-called "Kant's reply to Hume" in the Second Analogy of Experience, which is structured as a proof of the a priori character of (1), but whose implications for (2) remain controversial.